Minimization of radio resource usage in multi-hop networks with multiple routings

ABSTRACT

Packets in a multi-hop wireless network are routed based on the available link throughputs, network node congestion and the connectivity of the network in a manner that minimizes the use of radio resources and minimizes delay for packets in multi-hop system. The routing method also avoids congestion in the access network, especially near the network access points as provided by network access nodes. Each wireless network node maintains a link table for storing link conditions and associated route costs. Packets are routed according to the low cost route. Subsequent wireless network nodes evaluate whether a lower cost route is available and, if so, route the data packet according to the lower cost route. Every wireless network node transmits the data packet, a specified route and a time stamp indicated a time of the last data entry in the link table that was used to calculate the low cost route.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to and incorporates by reference and claimspriority under 35 U.S.C. 119 the following provisional applications forpatent:

-   -   1) U.S. Patent application Ser. No. 60/446,617 filed on Feb. 12,        2003, and entitled “System for Coordination of Multi Beam        Transit Radio Links for a Distributed Wireless Access System”;    -   2) U.S. Patent application Ser. No. 60/446,618 filed on Feb. 12,        2003, and entitled “Rendezvous Coordination of Beamed Transit        Radio Links for a. Distributed Multi-Hop Wireless Access        System”;    -   3) U.S. Patent application Ser. No. 60/446,619 filed on Feb. 12,        2003 and entitled “Distributed Multi-Beam Wireless System        Capable of Node Discovery, Rediscovery and Interference        Mitigation”;    -   4) No. 60/447,527 filed on Feb. 14, 2003 and entitled        “Cylindrical Multibeam Planar Antenna Structure and Method of        Fabrication”;    -   5) U.S. Patent application Ser. No. 60/447,643 filed on Feb. 14,        2003 and entitled “An Omi-Directional Antenna”;    -   6) U.S. Patent application Ser. No. 60/447,644 filed on Feb. 14,        2003 and entitled “Antenna Diversity”;    -   7) U.S. Patent application Ser. No. 60/447,645 filed on Feb. 14,        2003 and entitled “Wireless Antennas, Networks, Methods,        Software, and Services”;    -   8) U.S. Patent application Ser. No. 60/447,646 filed on Feb. 14,        2003 and entitled “Wireless Communication”;    -   9) U.S. Patent application Ser. No. 60/451,897 filed on Mar. 4,        2003 and entitled “Offsetting Patch Antennas on an        Omni-Directional Multi-Facetted Array to allow Space for an        Interconnection Board”;    -   10) U.S. Patent application Ser. No. 60/453,011 filed on Mar. 7,        2003 and entitled “Method to Enhance Link Range in a Distributed        Multi-hop Wireless Network using Self-Configurable Antenna”;    -   11) U.S. Patent application Ser. No. 60/453,840 filed on Mar.        11, 2003 and entitled “Operation and Control of a High Gain        Phased Array Antenna in a Distributed Wireless Network”;    -   12) U.S. Patent application Ser. No. 60/454,715 filed on Mar.        15, 2003 and entitled “Directive Antenna System in a Distributed        Wireless Network”;    -   13) U.S. Patent application Ser. No. 60/461,344 filed on Apr. 9,        2003 and entitled “Method of Assessing Indoor-Outdoor Location        of Wireless Access Node”;    -   14) U.S. Patent application Ser. No. 60/461,579 filed on Apr. 9,        2003 and entitled “Minimisation of Radio Resource Usage in        Multi-Hop Networks with Multiple Routings”;    -   15) U.S. Patent application Ser. No. 60/464,844 filed on Apr.        23, 2003 and entitled “Improving IP QoS though Host-Based        Constrained Routing in Mobile Environments”;    -   16) U.S. Patent application Ser. No. 60/467,432 filed on May 2,        2003 and entitled “A Method for Path Discovery and Selection in        Ad Hoc Wireless Networks”;    -   17) U.S. Patent application Ser. No. 60/468,456 filed on May 7,        2003 and entitled “A Method for the Self-Selection of Radio        Frequency Channels to Reduce Co-Channel and Adjacent Channel        Interference in a Wireless Distributed Network”; and    -   18) U.S. Patent application Ser. No. 60/480,599 filed on Jun.        20, 2003 and entitled “Channel Selection”;

This application also claims priority to and incorporates by referencethe following copending application being filed concurrently herewithhaving at least one inventor in common, which application is entitled“Self-Selection of Radio Frequency Channels to Reduce Co-Channel andAdjacent Channel Interference in a Wireless Distributed Network” andhaving a serial number 60/468,456, filed on May 7, 2003.

TECHNICAL FIELD OF THE INVENTION

This invention relates generally to wireless communication systems and,more particularly, to traffic routing between wireless network nodes anda network access node.

DESCRIPTION OF RELATED ART

The structure and operation of wireless communication systems aregenerally known. Examples of such wireless communication systems includecellular systems and wireless local area networks (WLAN), among others.Equipment that is deployed in these communication systems is typicallybuilt to comply with standardized operations, i.e., operating standards.These operating standards prescribe particular carrier frequencies,modulation types, baud rates, physical layer frame structures, mediumaccess control (MAC) layer operations, link layer operations, signalingprotocols, etc. By complying with these operating standards, equipmentinteroperability is achieved.

In cellular systems, a plurality of base stations is distributed acrossthe service area. Each base station services wireless communicationswithin a respective cell. Each cell may be further subdivided into aplurality of sectors. In most, if not all, cellular systems, carrierfrequencies are reused so that interference between base stations usingthe same carrier frequencies is minimized and system capacity isincreased. Typically, base stations using the same carrier frequenciesare geographically separated so that minimal interference results.Similarly, a plurality of WLAN base stations (often called AccessPoints) is distributed across the service area. And, the carrierfrequencies for these are also reused to minimize interference betweenaccess points.

Traditional wireless mobile networks include Mobile Station Controllers(MSCs), Base Station Controllers (BSCs) and Base Station TransceiverSets (BTSs) jointly operate to communicate with mobile stations over awireless communication link. The BSCs and BTSs collectively are referredto as BSs or base stations. The traffic from the user terminals is thenrouted across the network of base stations or access points to reach thedestination user or to reach another network where the destination useror service is located. In the design of these networks the optimumassignment of carrier frequencies and the routing of traffic across thenetwork are important factors in achieving the desired cost andperformance of the system.

Wireless cellular communication service providers, as well as Internetservice providers, are increasingly working together to provide seamlessend-to-end call connectivity across the various platforms to enableusers to establish point-to-point connections independent of terminaltype and location. Traditionally voice networks have paved the way forthe creation of data networks for carrying data packets that containinformation of all sorts including voice.

Today, there are many forms of packet data networks, including variousversions of the Internet in which a computer typically is coupleddirectly using a broadband access technology such as cable modems,digital subscriber line modems, etc. The next generation of cellularnetworks presently being developed is being enhanced from traditionalsystems to create the ability for mobile stations to receive andtransmit data in a manner that provides greatly increased throughputrates. For example, many new mobile stations, often referred to asmobile terminals or access terminals, are being developed to enable auser to surf the web or send and receive e-mail messages through thewireless channel, as well as to be able to receive continuous-bit-ratedata, including so called “streaming data”. Accordingly, differentsystems and networks are being developed to expand such capabilities andto improve their operational characteristics.

In addition to the ongoing efforts to provide wireless data accessthrough wireless cellular networks as described above, manydevelopmental efforts are directed to building home and office wirelesslocal area networks according to any one of a plurality of technologiesand protocols. For example, Bluetooth and IEEE 802.11(b) provide for 2.4giga-Hertz (GHz) band wireless networks. IEEE 802.11(a), on the otherhand, provides for local area networks using the bands between 5.15 and5.85 giga-Hertz (GHz). In a home environment, only one or two accesspoints may be needed to provide coverage for access to a wirelessnetwork node. In these and other environments, however with largercoverage areas, a multi-hop network is possible in which a plurality ofwireless network nodes are used to collectively define a path from amobile client to a destination node. Each intermediate wireless networknode serves as a relay to receive communication signals from onewireless network node and to transmit the received communication signalsto yet another wireless network node or network access node. Generally,a channel is established from each node to another defining the path tothe network access node, which, in turn, provides access to an externalnetwork, such as the Internet. The channel may also be from one wirelessnetwork node to another in the same network when the destination is auser associated with the wireless network node.

Multi-hop networks are often advantageous for providing network accessfor a wireless client regardless of the underlying network, whether itis a cellular network or a wireless local area network. One problem withmulti-hop networks, however, is that set-up and maintenance formulti-hop networks are labor intensive by their nature because thespecific channels between wireless network nodes have required beingmanually pre-defined prior to use. Another problem relates to routingtraffic through a multi-hop network in an efficient manner. In thesimplest routing for a multi-hop network, nodes route their traffic totheir nearest neighbor. In this routing plan, each node makes itsselection of routes based only on local information about which of itsneighbors is on the route towards the network access node. The packettraffic is forwarded in multiple hops with the choice of the next hopbeing made independently at each node. This simple process will assurethat a packet will always reach the network access node. It does not,however, minimize the transit delay or the usage of radio resourcesalong the route.

While the above procedure for routing traffic is simple and reliable, itdoes not route traffic in a manner to minimize radio resources. With theever increasing demand for continuous-bit-rate data such as streamingaudio and video, as well as the transfer of images and other largefiles, routing to minimize the use of radio resources is importantbecause it affects the overall capacity of the access network andminimizes delay. When a packet is transmitted over a link, radioresources in the form of time and spectrum are used. These resources arethus unavailable for handling another packet either at the same node or(due to possible radio interference) at other neighboring nodes.Accordingly, it is desirable to minimize the use of radio resources forthe routing of each packet so as to increase overall capacity of thenetwork.

When nodes in the access network have links to multiple neighbors thatmay have different routes to the network access node or destinationwireless network node, appropriate routes must be chosen for thepackets. While the simple choice of the nearest neighbor can be appliedto the multiple neighbor case, it has the disadvantage that there may bemore hops than required and so introducing unnecessary delay andconsuming excess radio resources. There may also be congestion oftraffic in nodes that are closest to the network access node.

A method and apparatus for routing is needed therefore that can choosefrom among the multiple routes in a way that minimizes the usage ofradio resources and the packet delay, compensates for congestion acrossthe network and adapts to changes in the network configuration.

BRIEF SUMMARY OF THE INVENTION

The method and apparatus of the present invention provide for routingpackets based on the available link throughputs, network node congestionand the connectivity of the network in a manner that minimizes the useof radio resources and minimizes delay for packets in multi-hop system.The routing method also avoids congestion in the access network,especially near the network access points as provided by network accessnodes. The routing method of this invention is distributed across thenetwork, is tolerant to varying availability of routing information, istolerant to errors in the routing tables and is adaptive to changes inthe network connectivity and capacity.

More specifically, in a cluster of radio local wireless network nodesthat are linked to a network access point (or node), it is likely thatone or more of the nodes will be able to establish radio links to morethan one of the neighbors in the cluster. The visibility of multipleneighbors will provide multiple options for routing the traffic towardsthe network access node or from the network access node towards thewireless network node. The traffic may be passed through severalneighbors in a (multi-hop) chain to reach the destination node (ornetwork access node). For this routing, decisions must be made, forexample, if the traffic should simply be routed through the nearestneighbor (for further forwarding) or if the node should route itstraffic beyond its immediate neighbors to reach as close as possible tothe destination. In this choice the node must also consider that therate of data traffic throughput on the various links will differ. Forexample, longer distance links reaching closer to the destination nodemay have a much lower throughput than the ones to the nearest neighbor(that is much closer). Transmission of packets on links closer to thenetwork access node may also be more efficient due to the concentrationof the traffic and the consequent lower radio operational overheadassociated with each packet.

The invention for the selection of a route achieves a balance betweenchoosing direct routings to achieve low delays and efficiencies to begained through concentration of traffic in intermediate nodes. Forexample, if a wireless network node may select a route to one of twodownstream wireless network nodes, a priority consideration is tominimize a number of hops to a destination network access node. On theother hand, transmission efficiencies must also be considered. If thelink to the farther wireless network node is significantly lessefficient because of interference or other path loss factors, it may bepreferable to select a route including a hop to the closer wirelessnetwork node even though such a selected route would include at leastone more hop in the route to the destination node (wireless network nodeor network access node).

As such, the invention includes a method and apparatus for minimizingthe use of radio resources when routing across the access network. Themethod and apparatus have, in general, three aspects. The first aspectis determining what links are available for routing across the network,the cost factors associated with each link and the development andupdating of a routing information table in each node. The second aspectincludes initiating a route based on a cost function and the informationin an initiating wireless network node's routing table about thenetwork. The third aspect is the updating of the routing while thepacket is in transit if the network conditions change from those used byprevious nodes to select the initial routing.

Together these three phases provide a robust and efficient method forrouting packets across a multi-hop, mesh connected network that providesmultiple routes to a destination. Link efficiency, congestion and othersuch parameters are calculated by the wireless network nodes based, atleast in part, on monitoring and evaluating time delays and error ratesfor data packets sent through the various links and routes. In oneembodiment, the time of transmission from the wireless network nodes isused to determine the delays that are experienced for packets transitingthe network.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a functional block diagram of a communication network formedaccording to one embodiment of the present invention;

FIG. 2 illustrates a functional block diagram of an access controller;

FIG. 3 is a flow chart illustrating operation of one embodiment of awireless network node according to the present invention;

FIG. 4 is a flow chart illustrating a method according to one embodimentof the invention;

FIG. 5 is a flow chart illustrating one aspect of a method according toone embodiment of the invention;

FIG. 6 is a flow chart illustrating one aspect of a method for receivingand routing a data packet according to one embodiment of the presentinvention;

FIG. 7 is a functional signal diagram illustrating one aspect of a datapacket header according to one embodiment of the present invention; and

FIG. 8 is a functional block diagram illustrating a wireless networknode formed according to one embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a functional block diagram of a communication network formedaccording to one embodiment of the present invention. A communicationnetwork 10 is configured to allow a plurality of mobile stations, suchas mobile stations 12 and 14 of a cellular network and a client 16 of awireless local area network (WLAN), to communicate with each otherregardless of geographic location as long as they are located an areathat is served by a service node (e.g., a wireless network node). Whileclient 16 may be any type of wireless communication device, one typicalclient 16 comprises a wireless host coupled to a data terminal thatreceives and transmits data for a particular application. Collectively,herein, the wireless host that transceives data for the wirelessterminal and the terminal are referenced herein as a client.Alternatively, a client may also comprise a terminal having wirelesscapability integrated therein.

As may be seen, each of the mobile stations 12 and 14 communicate by wayof a base station transceiver system (BTS) 18, a base station controller(BSC) 20, and a mobile switching center (MSC) 22. As is known by one ofaverage skill in the art, MSCs, such as MSC 22, provide networkswitching for cellular traffic according to a mobile station's location.More specifically, each MSC is coupled to at least one BSC, which, inturn, is coupled to at least one BTS. The operation of cellular networksas represented by MSC 22, BSC 20, and BTS 18 is generally known by oneof average skill in the art.

Continuing to examine FIG. 1, MSC 22 also is coupled to a data packetnetwork 24. Data packet network 24 includes any and all types of datapacket networks, including any one of the known Internets, includingthose that operate under IP.v6 protocols. Data packet network 24 isfurther coupled to a network access node 26. Network access node 26provides access to data packet network 24 for wireless network nodesthat couple directly to network access node 26 or that couple to networkaccess node 26 by one or more wireless network nodes to provide accessfor client 16.

Data packet network 24 is further coupled to network access node 26 byway of a wireline link (though a wireless link could be utilized).Network access node 26 is coupled, by way of wireless links, to wirelessnetwork nodes 28 and 30. Generally, the underlying technology orphysical layer enables network access node 26 to only communicatedirectly with wireless network nodes 28 and 30 in the describedembodiment. Wireless network node 28 is capable of communicating withwireless network nodes 32 and 34, as well as wireless network node 30.Wireless network node 30 is also coupled to wireless network node 34.Finally, wireless network node 32 is coupled to communicate withwireless network node 35. Wireless client 16 is within range and iscommunicatively coupled with wireless network nodes 34 and 35.

For the sake of simplicity, the network of FIG. 1 is depicted as havinga number of wireless network nodes that are distributed about the regionto be covered and are linked together, and to the main communicationsnetwork, with transit radio links. The term “node”, as used inconjunction with the description of the present invention, contemplatesa component having a co-located access and transit functionality or itmay include only transit functionality. The wireless terminalscommunicate with the nodes using the access radio links, and the trafficis forwarded between the wireless network nodes using the transit radiolinks to reach the network access node and the communications network.It is also possible for the traffic to be forwarded between the nodes toreach another terminal that is also attached to the same local areanetwork.

In the “uplink”, a packet flow is toward the communications network, andin the “downlink” the packet flow is toward the wireless network nodethat has coverage for the subscriber's terminal. Wireless access radiosystems of the type to which the invention is particularly usefultypically operate in packet mode, meaning they are only active(transmitting or receiving radio signals) when they are sending orreceiving a packet; otherwise, they are quiescent, “listening” fortraffic and occasionally exchanging signaling messages foradministration of the radio system, but otherwise quiet.

The nodes may have links to multiple neighbors and these may offeralternate routing for packets among the nodes and to the network accessnode. As illustrated in FIG. 1, wireless network node 34 may route itspackets towards the network access node 26 via any one of its neighborwireless network nodes 28, 30, or 32. Wireless network node 34 must,therefore, include logic for choosing an appropriate route and, moreparticularly, between wireless network nodes 28, 30 and 32. As thedifferent routes may have different delays and radio transmissionconditions, the choice of an optimum route must consider information onradio link performance and cost across the network.

In this wireless access system, a node in the form of a wireless networknode (routing point) is typically provided that features both access andtransit capabilities. Access capabilities are afforded by the provisionof one or more directional antennas for communication with wirelessterminals of a variety of different types (wireless enabled PDAs,personal computers, hybrid telephony-data terminals, and the like). Theaccess antennas can optionally be in the form of omni-directionalantennas, or an array of directional antennas arranged to provide up to360 degree coverage. Preferably, at least two access antennas areprovided per node for diversity purposes. Alternatively, the accesscapabilities can be provided by one or more directional antennas, in theevent it is desirable to have a more focused access coverage area.Transit capabilities are afforded by an array of directional antennasthat provide for directional communication with other nodes or, forexample, wireless backhaul. The provision of two or more directionalantennas is contemplated for the directional antenna array; preferablysix or more antennas are provided to afford a sufficient degree ofdirectionality for each antenna. The antennas of the directional arraypreferably also are arranged to include diversity, which may be in theform of space or polarization diversity. The use of polarizationdiversity has the advantage that a more compact array may beimplemented. In one embodiment, an antenna system having six dualpolarized directional antennas is used for transmitting along 1 of 6beams with a corresponding orthogonal polarization.

While FIG. 1 describes the multi-hop operation according to the presentinvention for client 16 and the wireless network nodes 28-35 that createa path or route to network access node 26, it is understood that theinvention applies with equal force to any other multi-hop configuration.For example, if a multi-hop topology is implemented to provide trafficroutes for mobile stations 12 or 14, the invention could be implementedtherefor as well.

In operation, client 16 establishes a communication link with one ofwireless network nodes 34 or 35. In the case of client 16 establishing alink with wireless network node 35, wireless network node 35 wouldinitiate the first link to wireless network node 32 only because it isnot communicatively coupled to any other wireless network node. Wirelessnetwork node 35, however, would generate route information fortransmission with the traffic (data packets) from client 16 defining thesubsequent wireless network nodes in a specified route to network accessnode 26. For example, the route information could specify that thetraffic be routed either through wireless network node 34 or 28 fromwireless network node 32. The subsequent wireless network node 28 or 34,upon receiving the traffic with routing information, compares therouting information to its own routing information and determines, incase of conflict or difference, which is more current. The subsequentwireless network node 28 or 34 then routes the traffic to the next linkaccording to the routing information that is most current. Downstreamwireless network nodes in the route to network access node 26 operate ina similar manner to create a route for data packets between client 16and, in the example of FIG. 1, data packet network 24. In this example,the originating wireless network node 35 has only one route available(to node 32). Node 35 need not do any routing, it could simply send allits traffic to node 32. Here, node 32 would contain the routinginformation and determine the most cost effective routing.

Each wireless network node of FIG. 1 includes an access radio system, atransit radio link radio system and a communications controller unit.The access radio system may use a bi-directional radio system, such asdefined by the IEEE 802.11 standard, or any other standard for wirelesscommunications, including any known cellular standard or other wirelesstechnologies, such as Bluetooth. Equipment for 802.11 and Bluetoothsystems is widely available and is of low cost. For conducting trafficbetween the access radio system and the appropriate transit link, thereis a communications controller unit that receives the packets (to/from)the access radio, stores them briefly (if needed) in suitable memory,determines the appropriate transit radio link, and forwards/receivesthem through the transit radio link to reach their destination. Thetransit radio system preferably utilizes a bi-directional standard suchas the IEEE 802.11, but operates at a different radio frequency to avoidinterference with the access radio system, i.e., the standard IEEE802.11(b) operates in channels in the 2.4 GHz radio band and the IEEE802.11 (a) operates in channels in the bands between 5.15 and 5.85 GHz.The access system is also applicable to other sets of frequencies forone or both the access and transit aspects of operation, and to theapplication of other radio system standards such as IEEE 802.16(a).

Using WLAN technologies such as 802.11 (as illustrated above) oralternatively using IEEE 802.16 is increasingly becoming a very costeffective means to deliver data service. Utilization of the teachings ofthe present invention—by providing efficient routing for packets —willprovide a cost effective solution for high rate data service to hotspots or selective areas.

This invention improves upon the capability of the existing standards(such as the 802.11) in a compatible way that enables the softwareupgrade of existing commercial devices to be used in the distributedmulti-hop wireless access system. This technique will enable a vendor'sproducts to better handle packets, including general data packets, aswell as Voice-over-IP and video services. This invention is applicableto and relates to any air interface such as cdma2000, UMTS, GPRS, andother air interface technologies. In general, the specific embodiment ofthe described invention includes the portion of the network of FIG. 1that comprises wireless local area network. The reference to wirelessnetwork nodes and, more generally, to nodes, should be considered toapply not only to wireless network nodes in a WLAN, but also tocorresponding access points of a cellular network.

FIG. 2 illustrates a functional block diagram of a wireless network nodewith circuitry to act as an access controller. The wireless network nodeof FIG. 2 represents any one of wireless network nodes 28, 30, 32, 34 or35. For simplicity, wireless network node 34 is specifically described.Wireless network node 34 includes an IEEE 802.11(b) radio 40, an 802.11(a) radio 42 and a communications controller unit 44. As may further beseen, communications controller unit 44 includes logic for creating arouting table in a multi-hop wireless network, logic for updating therouting table, logic for initiating packet routing and logic fordetermining whether to update and change packet routing for a receivedpacket. The specific details of the operation according to these logicblocks are as described in the process steps disclosed herein.

FIG. 3 is a flow chart illustrating operation of one embodiment of awireless network node according to the present invention. Generally, themethod of FIG. 3 illustrates a method for minimizing the use of radioresources when routing across the access network. Initially, a wirelessnetwork node (each wireless network node in the multi-hop network of thedescribed embodiment of the invention) evaluates link information (step46). This step generally includes evaluating link availability and cost.This step also generally includes periodic, or occasional updating,evaluated link availability and cost information.

More specifically, step 46 includes steps 48-54. Thus, the, wirelessnetwork node creates a link table (step 48), adds information to thelink table based on local link conditions (step 50), adds information tothe link table based on link information received from neighbors (step52) and, finally, adds a time of entry into the table each time thatdata is added or updated to the table (step 54). Accordingly, a type oftime stamp is utilized to enable wireless network nodes to determinewhich data is most current when preferred route information is inconflict, as will be described in greater detail below.

In addition to evaluating link information in step 46, the wirelessnetwork node (when initiating transmission of a packet), selects anoptimum route based upon the evaluations of step 46 and initiatestransmission on a first link of the selected optimum route (step 56).Generally, this step includes an initiating wireless network nodeselecting a route based on a cost function and the information in itsrouting table about the network. The initiating wireless network nodealso adds routing and time stamp information to the data that is beingtransmitted (step 58). Finally, the invention includes, if the wirelessnetwork node received a packet with routing information, determiningwhether a lower cost route exists than what is specified with thereceived routing information and, if so, transmitting the packet on alink for the newly determined route wherein the packet includes thenewly determined route information (step 60). Step 60 generally includesupdating the routing information while the packet is in transit if thenetwork conditions change from those used by previous nodes to selectthe initial routing. Together these steps) provide a robust andefficient means to route packets across a multi-hop, mesh-connectedmultiple route network.

With respect to step 46, evaluating link information includes developinga routing table for a multi-hop, multi-route network that is based on a“cost function” for each of the possible alternate routes in thedescribed embodiment of the invention. The radio resource cost for oneof the routes to the network access node may be simply the sum of theradio transmission time required for the packet for each hop in thechain to the network access point. The radio transmission time for alink may be calculated, for example, from the quotient of the packetsize and the data transmission rate for the link. The use of radioresources will be minimized if a routing is chosen that minimizes thissum. Thus, in the event that multiple routings are available, the nodemay evaluate the sum for each possible route and choose the route withthe minimum sum specified in the routing table. If there are multipleroutes to different network access nodes to the wired network (or to thedestination wireless network node), the minimum sum route should stillbe chosen to minimize the use of radio resources.

To determine the sum, the node must know the rates available on all thelinks' to the desired end node (which may be either another node in theaccess network or the network access node). This information may beobtained from the other nodes. Each node can determine the transmissionrate and efficiency for each of its links. The link information iscommunicated among the nodes by the exchange of messages. These messageswould report the latest availability of links and their data rates. Fromthis combination of information about its own links, together withinformation about other links received from other nodes in the network,each node would be able to construct a table of the available links inthe network and the data rate on each of these links and otherinformation about the links (as will be discussed later). Theinformation in this table would be shared among the neighbors to aidwith their routing plans. As the availability of the links and theirdata rates may change over time due to changing traffic conditions orradio interference, the table is updated as conditions change and thenew information exchanged with the nodes in the network. Thus, therouting would automatically be kept up-to-date with changing radioconditions, interference and link availability.

As mentioned earlier, the radio resources used for a packet is affectednot only by the transmission rate (which together with the size of thepacket determines the time required for transmission), but also by theefficiency of the link. As the radio transmission system requires thetransmission of some overhead information in addition to the packet, thecost of transmitting a packet may be reduced if the overhead can beshared among a group of packets sent together on a link. Thus, the tableof link information should include not only the transmission rate foreach link in the network, but also the efficiency of the link. Thisefficiency may be expressed as a factor that is used by the node tomultiply by the packet size-link rate quotient to determine the net costof the link.

As an example, a single packet sent over a link may incur a 30%overhead. So a link that is largely idle would have an efficiency factorof 1.3. Packets routed over this link would incur a cost increased by1.3 as they would bear the full overhead. A link that is already busywith packets would be able to spread the overhead over multiple packetsand so each would incur a lower overhead. A link that is already busywith traffic may thus have an efficiency factor of 1.05 indicating thatthere is only a 5% cost addition for routing a packet over that link.Thus, in measuring the performance of each link, the nodes would recordthe transmission rate together with the occupancy that may be recordedas an efficiency factor. This information for each link would beexchanged among the nodes in the network to enable the optimum routingto be selected.

This information about the links in the network is exchanged throughmessages among the nodes in one embodiment of the invention. Theinformation is transported together with the packets as they passthrough the networks in an alternate embodiment of the invention.Information about the quality of the links traversed along the routecould be added together with the payload packet (“piggy-backed”). Thenodes along the route would thus gain the most recent information on thelink conditions with each packet. This minimizes the overhead requiredfor transmission of the network information. In yet another embodimentof the invention, the system uses a combination of both piggy-backed anddedicated information packets. Some links may have little traffic andhence need dedicated messages to report their conditions, whilefrequently used links would be updated using the piggy-backedinformation packets. The traffic flows may be different in eachdirection of a link between two nodes, and so the link parameters (rateand efficiency) will need to be recoded in the link table separately foreach direction. As an example, the transmission rate and efficiency fora link from a first node to a second node will be different than thetransmission rate and efficiency for the link from the second node tothe first node.

The delay experienced by packets as they pass through the nodes in thenetwork is another measure of performance. The delay a packetexperiences in a node may be caused, for example, by queues as thepacket, or a group of packets, waits for the transit radio link tobecome available. They also may be delayed because the radio unit in thenode may be busy communicating other packets to other nodes. The bestroute for the packet should also minimize the delay in transiting thenetwork. Thus, the information exchanged among the nodes about the linkperformance should also include the node delay for packets on the links.This information may also be summed for each possible route by the nodewhen choosing a route and the routing selected that minimizes the costof radio resources and delay chosen. This might be, for example, bychoosing the route with the lowest product of radio resource cost sumand the delay sum.

As the network connections and radio conditions change over time,information in the table may be updated. Some information in the tablemay also become out-dated or even invalid due to changes in the networkover time. To compensate for possible errors in the routing table, thetable should also include an entry indicating the time the table entrywas made.

The above-described embodiments utilize a table for the collection ofthe routing information held by each node in the network. One of averageskill in the art may readily determine how to create a data structurefor functionally creating such a table or for storing such data.Alternatively, lists of link parameters or integration of theinformation as parameters in the associated operating program may beused to implement the routing concepts of this invention. Alternatively,a database structure may be used.

The wireless network node initiating the routing of a packet in step 50selects a route based on the information available in its routing table.A routing that minimizes the use of radio resources is selected bychoosing the route that has the minimum sum over each link in the routeof the packet transmission time multiplied by the efficiency for thelink. The initiating node may determine the cost for each route bysumming the entries for that route in its routing table, and selectingthe one with the lowest cost and delay. The packet would then be sent tothe first neighboring node in the chosen route. The packet isaccompanied by additional information, according to step 52, concerningthe source node, the end node, the proposed routing, and the time of themost recent information in the table used to develop the route in thedescribed embodiment of the invention.

The above discussion assumes, however, that there is no congestion atany of the nodes along the route to the desired end node. With thetraffic flowing towards the network access point, it is to be expectedthat the nodes in the neighborhood of the network access point (and thenetwork access node itself) may become saturated (a node's radioresources are fully occupied with its established links and traffic andno additional links can be maintained). The congestion may occur, forexample, as each possible link that is maintained by a node-pairconsumes some radio resources, even if there is no traffic flowing overthe link. This reduces the traffic capacity that the node can provide toother nearby nodes. The nodes near the network access point cannotafford to maintain links to all their visible neighbors as this would beinefficient (as all the radio resources may be occupied maintaininglinks without room for traffic). Thus, when considering the routing, thenode must also consider the congestion along the route.

Thus, the route is selected in step 50 that has the minimum cost to anode that is not congested and that is already linked to the congestednode that is closest to the desired end node (or the receiving end nodeitself). This choice minimizes the use of radio resources and packetdelay and also minimizes congestion at the nodes nearest the networkaccess point.

This routing to a node neighboring the congested node avoids directlyadding congestion to the congested node. As there is already trafficfrom the neighbor to the congested node, the additional packet may beadded most efficiently to the existing traffic. Choosing the neighboringnode allows the traffic to be sent to the congested node using anexisting link and hence without causing it to use extra resources tosupport another (new) link. This choice has the effect of backing offthe congestion to the next node in the route.

When initially routing a packet, the node may consider network factorsin addition to the usage of radio resources along the route. To avoidcongestion, the routing may also be selected to balance the flow oftraffic across multiple links. Thus, if the information in the routingtable indicates that more than one route may be used with equivalent (ornearly equivalent) cost, the node may select the route to balance theflow of traffic among the possible routes.

When a node receives a packet from a neighbor, as specified in step 60,for forwarding onwards across the network, the node evaluates theproposed routing against its own version of the network routing table.The node calculates the cost and delay sum of the route proposed by thesender and compares this against the alternatives (if any) in its table.If the node's table includes more recent information than the sender's(as determined by a time stamp in the node's own routing table incontrast to a time stamp received with the packet from the neighbor),and a lower cost route is found, the node may elect to change therouting information received with the data packet based on the new costsum from its own routing table. Generally, the node uses the routingtime information provided by the sender together with the packet tojudge if its routing table information supersedes the routing selectedby previous nodes. The packet is then forwarded to the next node in theroute, together with the routing information (either the original if theroute is not changed or the new information if it is changed).

Each wireless network node along the route, in the described embodimentof the invention, includes logic to prompt it to re-evaluate the routingand to make adjustments if the wireless network node has additionalrouting information or the network conditions have changed while thepacket was in transit. This aspect makes the routing robust againsterrors in the routing tables in the network nodes and adaptive tochanges in the network capabilities. This aspect also allows the networkto include nodes with widely varying amounts of information in therouting tables (or even operate with nodes that contain a very simple(minimal) local routing table). As long as the node can forward a packetto another node along the route, or initiate a route by sending a packetto its appropriate neighbor, when the packet passes through a node withadditional routing information, the routing will be adapted to thelatest optimum conditions of the network. Thus, the network is maderobust to routing information and changes in the capability andconnectivity.

The nodes and the network may function with routing table informationthat ranges from simply information about the nearest neighbors toincluding information for a full network map and capability. The timelyupdating of the information in the routing tables is not critical to thesuccess of the routing across the network. If a node in the proposedrouting becomes inoperative, the routing will be altered by other nodesalong the route as they become aware of the changed network structure.Thus, the routing of packets will automatically adapt to changes thatoccur in the network after their initial routing is selected, or if theinitial routing was based on invalid information in the routing table.The routing tables may be updated at a later time (perhaps triggered bythe observed change of routing) and so there is no dependency on timelydistribution of routing information to maintain optimum routing ofpackets.

With traditional routing processes, with each node re-evaluating andpossibly changing the routing of the packets, there is a danger ofcircular routing (i.e., the packet may be re-routed back to theinitiating node, where it would be re-routed out along the originalpath, causing it to be re-routed back to the start again, etc.). This isundesirable as the packet will fail to reach its destination and may beendlessly circulated about the network consuming resourcesunnecessarily. There are a number of methods that are traditionallyapplied to prevent circular routing. For example, when a node isre-routing a packet it should check that the new route does not includethe initial source node of the packet. The node can make this check asthe initial node is included as part of the routing information sentwith the packet. If the proposed new route does include the source node,then another alternate route should be selected. However, this solutionrequires that the re-routing node perform extra processing to check forpossible circular routing.

The invention described herein precludes circular routing through theuse of the timing information included with the packets. The packets aresent together with information about the time of the latest informationused to develop the route (as described above). Nodes along the routewill only re-route the packet if they have more recent information aboutthe links for the route. If they do re-route the packet, they willindicate the new time of the routing information together with thepacket. Thus, even if a re-routing does cause the packet to travel backto its source node, the source node will not change the routing as itsinformation will be superseded by the updated routing time informationprovided with the packet (unless, of course, the source node has evenmore recent information about the route). In addition to preventing,circular routing, this method also allows the network to better respondto changes in the connectivity in that changes in routing as a result ofloss of links can be accommodated by freely re-routing around the brokenconnections.

The routing table is contained in memory of the communicationscontroller unit 44 of FIG. 2 and contains information used by therouting processes. The routing table contains information about theroutes available between nodes in the network, the cost of these routesin terms of data rate and efficiency, and the time the route informationwas measured. The table may contain information about all the routespossible in the network, or it may contain less information. Some nodesmay operate with a table that only contains information about routes toa few of their nearest neighbors.

The routing update process is used both to fill in the information inthe table initially and to update the table based on local measurementsor information received from other nodes in the 16 network. Initially,the table will contain only information about the links from the node toits nearest neighbors. As the node exchanges information with theseother nodes, it will be able to also make entries about the cost (forexample, rate and efficiency) of these links. As the link costinformation becomes available to the node it will enter it in the tableand will send it to its neighboring nodes in the network. The node willalso receive information from other nodes in the network about availablelinks and their cost in other places in the network. The routing tableupdate process will enter this new information in the table (togetherwith time information). The entry of information into the routing tablemay be achieved in a plurality of manners. The information about thelinks discovered for the neighboring nodes may be used to form the basisfor the entries in the routing table.

The initial packet routing process is used to route packets that havebeen received by the node from its access links. The initial routingprocess will choose a route based on the information in the routingtable and choose a route that minimizes the route cost (as describedpreviously). The packet will then be sent to the appropriate neighboring(or distant neighbor) node to begin its journey.

The transit packet routing process is used to check the routing andforward packets received over the transit links to the node from itsneighbors. This will occur according to the process described previouslyunder the third aspect of routing. The packet will then be sent to theappropriate neighboring node to continue its journey. If the nodedecides to re-route the packet as a result of more or later informationin its routing table, the transit packet routing process may use aspectsof the initial routing process to select the new routing.

FIG. 4 is a flow chart illustrating a method according to one embodimentof the invention. Initially, a wireless network node creates a linktable describing cost and efficiency information (step 61). The wirelessnetwork node adds information to the table based on local linkconditions (step 62). The wireless network node also adds information tothe table based on link information received from neighbor wirelessnetwork nodes, i.e., neighbors (step 64). Each time the wireless networknode adds information to the table, the wireless network node adds atime stamp, or time of entry information to the table (step 66).Finally, the process of FIG. 4 includes sending information about linksincluding time of entry to neighbor wireless network nodes (step 68).Each of the steps described herein are similar to what was describedpreviously.

FIG. 5 is a flow chart illustrating one aspect of a method according toone embodiment of the invention. Initially, a wireless network nodecreates an initial route for a packet (step 70). The wireless networknode then evaluates a cost function for each possible route to a networkaccess node (step 72) and selects the lowest cost route (step 74). Uponselecting the lowest cost route, the wireless network node adds routeand time of route information to the packet(s) (step 76) and sends acombined packet having traditional header information and the addedheader information onto the first link of the selected route (step 78).Each of the steps described herein are similar to what was describedpreviously.

FIG. 6 is a flow chart illustrating one aspect of a method for receivingand routing a data packet according to one embodiment of the presentinvention. Initially, a wireless network node receives a data packet(step 80). The wireless network node then examines route informationreceived with the data packet to determine a destination of the packet(step 82). The wireless network node further examines a received timestamp that was received with the data packet (step 84). The wirelessnetwork node then determines if there is a difference in the receivedroute information and wireless network node's stored route information(previously stored in the link table) to the network access controller(or final destination within the multi-hop network) and, if so, whetherthe access controller's stored route information has a lower cost aswell as a more recent time stamp (step 86). If so, the wireless networknode re-routes the data packet accordingly along the route with thelowest cost as defined within its own link table (step 88). The wirelessnetwork node further adds new time information to the packet (step 90)and sends the data packet on the first link of the new route (step 92).If the wireless network node does not determine that there is adifference in the received route information or if the received routeinformation has a more current time stamp, the wireless network noderoutes the data packet according to original route information receivedwith the packet (step 94).

FIG. 7 is a functional signal diagram illustrating one aspect of a datapacket header according to one embodiment of the present invention. Adata packet header 96 comprises a source address field 98 for storing anaddress of an original source that is transmitting the data packet. Adestination address field 100 for storing a destination address of afinal destination packet. Additionally, the signal data packet header 96includes a route plan field 102 for storing the route plan, a time ofinformation field 104 for storing a time stamp reflecting when the linktable from which the route plan was derived was last updated, and anefficiency field 106 for transmitting data relating to networkefficiency. The use of an efficiency field 106 is optional and isutilized in only some embodiments of the present invention. In oneembodiment of the invention, for example, efficiency field 106 carriestime of transmission data for at least one wireless network node so thatthe timing for transmission through a link may be determined as a; partof calculating a link's efficiency. In another embodiment, at least twotime values are transmitted within efficiency field 106. A first timevalue reflects one of a total transmission time that is updated by everywireless network node or a transmission'time of the initiating node sothat a total time may be calculated. A second time value reflects thetransmission time of the data packet from the previous' wireless networknode. Accordingly, a wireless network node or a network access node mayevaluate the value(s) in the efficiency field to determine a total routeefficiency as well as an efficiency of a previous link.

While FIG. 7 illustrates the use of an optional efficiency field 106,some of the data contemplated for transmission therein may also betransmitted in a separate data word or alternatively as a part of adifferent field. For example, time of transmission or total transmissiondata may be transmitted along with the routing data wherein eachwireless network node updates transmission time data as a data packeteither is received or transmitted to support the same types ofefficiency calculations.

In one embodiment, the route plan stored in route plan field 102includes a list of the sequence of nodes the packets are to traverse toreach their destination. The time stamp stored in time of informationfield 104, in one embodiment, includes the time of the information usedin developing the route. The routing sequence does not include the planfor the links already traversed in one embodiment. Thus, the list of thesequence of nodes (the route plan) would shrink (by one entry) at eachintermediate node in the route. This arrangement would be preferable asit reduces the amount of extension information to be transported. Thetime information should preferably include the time of receipt at theoriginating (or re-routing) node of the cost function information foreach of the links in the proposed route.

With the described header information, intermediate nodes are able todevelop re-routing plans when they have more recent information aboutany of the links in the proposed route. This further enables optimalre-routing as the intermediate nodes would be able to re-evaluate eachlink in the route. However, in order to reduce the amount of informationtransmitted for the routing process, in one embodiment, time ofinformation field 104 includes just a single time reflecting the mostrecent information used in developing the route. This enables theintermediate nodes to re-route only if they have information about alink in the route that is newer than the newest information at theoriginating (or re-routing) node. This approach would be less optimal inrouting, but more economical in the amount of information transportedacross the network. Alternatively, a plurality of time stamp values maybe provided reflecting the time that any one link status was updated inthe link table of the originating and intermediate wireless networknodes.

The routing and timing information could be sent together with thepackets in the network in a number of ways. In one embodiment, therouting and timing information is appended to the information to thepackets being sent and is marked as an extension to the standard header.In a general network, some of the intermediate nodes may not be equippedwith the necessary routing capabilities to make use of the extendedinformation. These nodes would ignore the extension information in theheader, and pass along the packet according to their usual process(e.g., based on destination address route to the next neighbor in thatdirection). Intermediate nodes that are equipped with the additionalrouting capabilities are able to recognize the extension information andmake use of it to confirm or alter the routing as they determine fromtheir most recent routing information and the extension informationincluded with the packet.

FIG. 8 is a functional block diagram illustrating a wireless networknode formed according to one embodiment of the invention. A wirelessnetwork node 110 includes a processor 112 that is coupled to receivecomputer instructions stored within a memory 114 and, more particularly,within a memory portion 116 that includes computer instructionsretrieved from memory 114 by way of a bus 118 that define operationallogic for selecting a route as described herein. Generally, memory 114includes computer instructions that define operational logic for thewireless network node including instructions that relate to routineoperations of the wireless network node. Additionally, the computerinstructions in memory portion 116 define logic as described in each ofthe above described method steps and logic to result in operation asdescribed according to the various embodiments of the inventionincluding, for example, the operation of wireless network nodes asdescribed in relation to FIGS. 1-7 herein. Generally, the computerinstructions include logic for the wireless network node to create andupdate a link table (or equivalent thereof), to route traffic and datapackets according to a lowest cost route, to generate route and timestamp information with the data packets and to update or modify aspecified route for a data packet under specified conditions describedherein this application.

The invention disclosed herein is susceptible to various modificationsand alternative forms. Specific embodiments therefore have been shown byway of example in the drawings and detailed description. It should beunderstood that the drawings and detailed description thereto are notintended to limit the invention to the particular form disclosed, but onthe contrary, the invention is to cover all modifications, equivalentsand alternatives falling within the spirit and scope of the presentinvention as defined by the claims. For example, if base stations areinterconnected with wireless links, their operation could readily bemodified to included the inventive concepts disclosed herein in whichthe wireless network nodes in the description operate according to CDMA(or GSM or AMPS) radio standards acting as the access radio (instead ofthe 802.11 as disclosed herein). Alternatively, if a fiber interconnectis used among the base stations (or wireless network nodes) in a mesh,then the same principles could be used for choosing a route among themultiple routes provided by the fibers or the channels in the fibers.

What is claimed is:
 1. A method for creating a network information tablefor a network node, comprising: determining link conditions from locallink conditions to the network node, the link conditions includingtransmission rate, efficiency, and node delay information for each linkof a plurality of links available to the network node; receivingdetermined neighboring link conditions from neighboring wireless networknodes available to the network node, wherein the determined neighboringlink conditions include transmission rate, efficiency, and node delayinformation for links of each of the neighboring wireless network nodesof the network node; producing the network information table based uponthe determined link conditions and the received determined neighboringlink conditions; transmitting the network information table to theneighboring wireless network nodes; and when the determined linkconditions or the received determined neighboring link conditionsindicate a network condition change; updating the network informationtable with the determined link conditions and with a time stampindicating a table update time, wherein the time stamp facilitates tocompensate for possible errors in the network information table; andtransmitting the updated network information table to the neighboringwireless network nodes.
 2. The method of claim 1 further comprising:selecting a route for a data packet wherein the route has a link costthat is lower than any other route based on information in the networkinformation table.
 3. The method of claim 2 further comprising:forwarding the data packet onto a first link to a first hopcorresponding to the selected route.
 4. The method of claim 3 furthercomprising: transmitting route information with the data packet.
 5. Themethod of claim 4 wherein the route information is placed in an appendedheader.
 6. The method of claim 4 further comprising: transmitting asecond time stamp corresponding to the route information.
 7. The methodof claim 6 wherein the second time stamp corresponding to the routeinformation is placed in an appended header.
 8. A method for selecting aroute in a multi-hop network for a data packet at a node communicatingwith a wireless network node device, the method comprising: generating anetwork information table at a source node, the network informationtable including link information on one or more available links from thesource node to a destination node, the link information on the one ormore links including the linked nodes, transmission rate between thenodes, efficiency of the link, a node delay, and a time stamp indicatingwhen the link information was determined, wherein the time stampfacilitates to compensate for possible errors in the network informationtable; calculating a cost of available routes for the data packet fromthe source node to the destination node, the cost calculated by summingthe quotient of the packet size and the transmission rate multiplied bythe efficiency of the link for the nodes of the available routes to thesource node; determining a lowest cost route based upon the calculationof cost of available routes; storing a second time stamp indicating whenthe lowest cost route was determined; and transmitting the data packetwith information regarding the lowest cost route and the second timestamp.
 9. The method of claim 8 wherein the data packet is transmittedonto a first link of the determined lowest cost route.
 10. The method ofclaim 9 wherein the determined lowest cost route and the second timestamp are transmitted as a part of a header of the data packet.
 11. Themethod of claim 9 wherein the determined lowest cost route and thesecond time stamp are transmitted as a part of an appended header of thedata packet.
 12. The method of claim 9 wherein the determined lowestcost route and the second time stamp are transmitted as a part of adedicated signal for transporting route and time stamp information. 13.A method at an intermediate node for rerouting a data packet receivedfrom a source node to a destination node, the method comprising:providing a network information table at the intermediate node, thenetwork information table including link conditions of the intermediatenode, and including neighboring link conditions of neighboring wirelessnetwork nodes, the link conditions and the neighboring link conditionsincluding transmission rate between the nodes, efficiency of the link, aqueue delay, and a time that the link information was determined;calculating, based upon the network information table, a cost ofalternate routes available to the intermediate node to an original routefor the data packet from the intermediate node to the destination node,the cost calculated by summing the quotient of the packet size and thetransmission rate multiplied by the efficiency of the link, wherein thedata packet includes route and time stamp information indicating whenthe original route was determined; determining whether each of thealternate routes has a lower cost than the original route; determiningwhether the intermediate node has more recent network information thanthat used to determine the original route in the source node; and whenthe intermediate node has more recent network information, transmittingthe data packet along an alternate route of the alternate routes havingthe lowest cost route.
 14. The method of claim 13 further comprisingtransmitting a new lowest cost routing information along with the datapacket.
 15. The method of claim 13 further comprising transmitting atime of the new lowest cost routing data.